Syrian rebel group once backed by the US beheaded a child on video

Rebel fighters aim their weapons as they demonstrate their skills during a military display as part of a graduation ceremony at a camp in eastern al-Ghouta, near Damascus, Syria July 12, 2015. Bassam Khabieh/Reuters Members of a Syrian rebel group that was once backed by the United States beheaded a young child in Aleppo, newly surfaced video footage has revealed.

The video of the child's murder shows a fighter pushing the boy down in the flatbed of a pickup truck then sawing his head off with a knife, Reuters reported Wednesday.

An earlier video filmed before the killing shows fighters in the back of the truck taunting the boy who they said was from a pro-government Palestinian faction that fights in support of Syrian President Bashar al-Assad.

"This is a prisoner from the Quds Brigade. They don't have men any more so they've sent us children today," one men said.

"These are your dogs, Bashar, children of the Quds brigade," said another.

The Quds Brigade denied that the 12-year-old child was one of its fighters.

The Syrian Observatory for Human Rights said the men in the video were fighters with the Nour al-Din al-Zinki Movement, which has received financial and arms support from the United States. The group no longer receives American backing.

The group condemned the beheading, describing it as a "human rights abuse" that did not reflect its beliefs.

"All individuals who undertook the violation have been detained and turned over to the committee for investigations in accordance with the relevant legal standards," the group said in a statement.

U.S. State Department spokesman Mark Toner called the report "appalling" and said the government was investigating the incident.

"If we can prove that this was indeed what happened and this group was involved … it would give us pause about any assistance or any further involvement with this group," he told reporters.